Dunno, but "db" usually denotes a database file of some sort. Whatever it is, it probably doesn't belong under your / (root dir). I'd open it in TextWrangler or other text editor and check out the contents (try the Hex Dump command if it's all garbled). That may or may not provide a clue.

MacRumors attracts a broad audience
of both consumers and professionals interested in
the latest technologies and products. We also boast an active community focused on
purchasing decisions and technical aspects of the iPhone, iPod, iPad, and Mac platforms.